Process which enables the reproduction of images by means of diazoic compounds to beobtained



Patented Mar..9, 1943 PROCESS WHICH ENABLES THE REPRODUC- TION OF IMAGES BY DIEAN S OF DIAZOIC. COMPOUNDS TO BE OBTAINED Emilien Barde, Paris, France; vested in the Alien Property Custodian No Drawing. Application November 17, 1939, Serial No. 305,040. In France November 19,

Diazotypic processes consist of creating on a suitable background azoic colors in generalin places untouched by light.

2 Claims.

These azoic colors result from mixing a diazoic compound with an azoic compound. Thi operation, known as coupling, has up till now required the help of reagents called developers for its practical success; the developer is gaseous (ammonia) if the azoic compound is associated with a diazoic compound on the background, the developer is liquid if the diazoic compound-is alone on the background; this liquid developer is then constituted by the association of an azoic compound with a suitable alkali.

Another process is based. on the auto-coupling properties of certain diazoics in connection with their photolysis products.

In this case, an exposure to slightly actinic light, under a drawing, partially decomposes the diazoic in the places touched by the light; a phenol is formed which couples spontaneously with the non-photolysed part of the diazoic, and the part of the proof not protected by the drawin assumes a deeper color. -A second exposure to a strongly actinic light, the drawing being withdrawn, entirely destroys the diazoic that has so far been protected, and the outline appears in white on a dark background. A negative is definitely obtained from a positive.

By making use of the known reaction of the auto-coupling of a diazoic with its photolysis phenol, the present invention enables a positive to be obtained from a positive.

According to the invention, known as the Frangialli process, the process consists of first of all using a strongly actinic light, under a tracing, then a slightly actinic light, with the tracing withdrawn.

The following describes the operation:

A paper impregnated with a solution of a diazoic of the above-mentioned type is exposed to a strongly actinic light, for instance, to the rays of a carbon arc lamp, the paper being under a drawing. The drawing is removed and the proof is then exposed to a slightly actinic light (Woods light, or reduced daylight, or rays of a. high pressure mercury vapor tube) or else, for a short period. to the former strongly actinic source of light. It is advisable to dampen the paper between the two exposures. Underthe action of this second exposure, the outline becomes colored, either spontaneously, or after remaining in the dark for a few seconds.

of the light to pass through, a single strongly actinic exposure is sumcient, and the outline appears after remaining a few minutes in the dark. In this manner a direct image in colored lines is obtained on a white background and the proof During the first strongly actinic exposure, un-

der the drawing, the diazoic is completely destroyed in the places touched by the light.

'During the second slightly actinic exposure, without the drawing, the diazoic that had been protected by the lines of the drawing is prac- .tically decomposed in phenol by the feeble rays; in view of the strong aflinlty of the subsisting diazoic for its photolysis product, there is immediate coupling and coloring of th line in most cases. In the other cases, this coloring takes place more slowly by exposure to the air in the dark.

The power andthe quality of the source of light areregulated so that the ratio of the phenol produced to the subsisting diazolc forms the theoretical molecular ratio for obtaining the maximum of coloring intensity.

Humidityhelps this reaction. It is therefore better to dampen the back of the proof with 7 solution. The paper coated with a 20% diazoic solution containing 5 to 10% of urea, is exposed.

under a tracing to the light of a carbon arc lamp. After the drawing is removed, the proof is exposed to a. feeble light (Woods light, for instance), then heated to 90-100 centigrade. The urea, by decomposing with the heat, liberates Y ammonia gas, which, by taking up the acid In the particular case of pencil drawings, where the line is only slightly opaque and allows part image.

the imidazol derivates and, in particular, the' diazoic of C. methyl amino 4. naphthimidazole. This product gives a .particularly sharp violet The invention therefore deals more particularly with the applicationin view of the abovementioned process-of the imidazols and, in particular, of C methyl amino 4 naphthimidazole.

Iclaim: v

1. The'method of directly obtainingpositive images of a positive drawing on a translucent sheet; comprising preparing a sheet having a sensitive film containing the diazonium compound produced from C. methyl amino-*i-naphthimidazole which is capable of coupling with prodnets of its photolysis to give a colored compound, exposing the film to highly actinlc light while under a translucent positive, removing the posithis from said film, and exposing the film to a lightly actinic source of light.

2. The methodof directly obtaining positive images of a positive drawing on a translucent sheet comprising preparing a sheet having a sensitive film containing the diazonium compound produced from C. methyl amino-4-.naphthimidazole which is capable of coupling with products of its photolysis to ive a colored compound, preparlng a drawing having lightly translucent lines traced on a highly translucent supporting sheet, and exposing the film to actlnic light while covered by said drawing.

EMILIEN BARDE 

